Curable composition

ABSTRACT

The invention provides a curable composition which comprises a polyoxyalkylene polymer having a reactive silicon group and a (meth)acrylate copolymer and exhibits excellent weather resistance for a prolonged period. This composition comprises 100 parts by weight of a polyoxyalkylene polymer (A) having at least one silicon-containing functional group capable of causing crosslinking through the formation of a siloxane linkage and 20 to 1000 parts by weight of a (meth)acrylate copolymer (B) having a hindered amine structure.

This application is a 371 national phase application of PCT/JP02/12477filed on 29 Nov. 2002, claiming priority to JP 2001-364015, filed on 29Nov. 2001, the contents of which are incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a curable composition containing apolyoxyalkylene polymer having a functional group containing a silicon(hereinafter referred to as a reactive silicon group in some cases)which can be crosslinked by forming a siloxane bond, and a (meth)acrylicester copolymer. The (meth)acrylic esters in the present inventioninclude acrylic esters and/or methacrylic esters.

BACKGROUND ART

Polyoxyalkylene polymers having a reactive silicon group have beendisclosed in, for example, Japanese Unexamined Patent ApplicationPublication Nos. 61-141761, 61-218632, 61-233043, 1-171683, 1-279958,and 10-060253.

Room-temperature curable compositions which react with moisture in theair to cure into a rubber form are stable in storage, weather-resistant,heat-resistant, and contamination-resistant, and broadly used assealant, adhesive, coating material, and so forth accordingly.Polyoxyalkylene polymers having a reactive silicon group areweather-resistant and suitable for sealant. However, as nice appearanceis increasingly desired for housing, further enhanced weather resistanceis desired.

In order to enhance the weather resistance, for example, JapaneseUnexamined Patent Application Publication Nos. 61-233043 and 2001-164236have disclosed a technique of compounding an additive-type UV absorbentor light stabilizer. However, since the additive-type UV absorbent andlight stabilizer bleed to the surface, it is difficult to maintain theweather resistance over a long period.

In order to enhance the weather resistance, for example, JapaneseUnexamined Patent Application Publication No. 59-122541 has disclosed atechnique of blending an acrylic copolymer with a polyoxyalkylenepolymer having a reactive silicon group, and says that this techniquecan significantly improve the weather resistance. However, it has foundthat long-time exposure degrades the weather resistance. Accordingly,still further enhanced weather resistance is desired.

Japanese Unexamined Patent Application Publication No. 2001-234072 hasdisclosed a modified silicone room-temperature curable compositioncontaining: (A) 100 parts by weight of a modified siliconeroom-temperature curable polymer having a reactive silyl group and whoseprincipal chain is polyether; (B) 0.01 to 20 parts by weight of a silanecompound containing an amino group; (C) 2 to 20 parts by weight of amacromolecular UV absorbent containing 0 to 2 percent by weight of apolymerizable hindered amine compound as a constitutional unit; and (D)0.01 to 20 parts by weight of a tin curing catalyst. Although thiscompound helps prevent the UV absorbent and the light stabilizer frombleeding, effectively, it does not lead to a sufficiently enhancedweather resistance, which has recently been desired.

SUMMARY OF THE INVENTION

In view of the above-described circumstances, the object of the presentinvention is to enhance the weather resistance over a long period ofcurable compositions containing a polyoxyalkylene polymer having areactive silicon group and a (meth)acrylic ester copolymer.

The inventors of the present invention have conducted intensive researchto overcome the above-described disadvantages, and consequently foundthat the weather resistance of a curable composition containing apolyoxyalkylene polymer having a reactive silicon group and a(meth)acrylic ester copolymer having a hindered amine structure isdramatically improved in comparison with that of a system in which ahindered amine compound is simply added to a combination of apolyoxyalkylene polymer having a reactive silicon group and a(meth)acrylic ester copolymer.

Specifically, the present invention relates to a curable compositioncontaining: 100 parts by weight of polyoxyalkylene polymer (A) having atleast one functional group containing silicon which can be crosslinkedby forming a siloxane bond; and 20 to 1,000 parts by weight of a(meth)acrylic ester copolymer (B) having a hindered amine structure.

Preferably, the (meth)acrylic ester copolymer (B) is prepared bycopolymerizing a reactive hindered amine compound expressed by Formula(I).

Formula (I):

(where R¹ represents a hydrogen atom or an alkyl group having a carbonnumber in the range of 1 to 18, R² represents a hydrogen atom or a cyanogroup, R³ represents a hydrogen atom or an alkyl group having a carbonnumber of 1 or 2, R⁴ represents a hydrogen atom or an alkyl group havinga carbon number of 1 or 2, and X represents an oxygen atom or an iminogroup).

More preferably, at least one of (meth)acrylic ester monomer unitsconstituting the (meth)acrylic ester copolymer (B) has an alkyl grouphaving a carbon number of 8 or more.

Still more preferably, the (meth)acrylic ester copolymer (B) is preparedby copolymerizing a vinyl monomer having a reactive silicon group.

Still more preferably, the functional group containing silicon of thepolyoxyalkylene polymer (A) is a reactive alkoxysilyl group.

DETAILED DISCLOSURE OF INVENTION

The polyoxyalkylene polymer (A) used in the present invention(hereinafter referred to as the polyoxyalkylene polymer (A)) is shown inJapanese Examined Patent Application Publication Nos. 45-36319,46-12154, and 49-32673, and Japanese Unexamined Patent ApplicationPublication Nos. 50-156599, 51-73561, 54-6096, 55-82123, 55-123620,55-125121, 55-131022, 55-135135, and 55-137129.

Preferably the chain of the polyoxyalkylene polymer (A) is constitutedof a repeating unit expressed by Formula (II):—R⁵—O—  (II)(where R⁵ represents a divalent organic group, preferably a divalenthydrocarbon group, and most preferably most groups represented by R⁵ arehydrocarbon groups having a carbon number of 3 or 4). Exemplary groupsrepresented by R⁵ include —CH(CH₃)—CH₂—, —CH(C₂H₅)—CH₂—, —C(CH₃)₂—CH₂—,and —CH₂CH₂CH₂CH₂—. While the chain of the polyoxyalkylene polymer (A)may be formed of a single type of repeating unit or at least two typesof repeating unit, R⁵ is preferably —CH(CH₃)—CH₂—, particularly from theviewpoint of appropriately reducing the viscosity of the polymer andgiving a suitable flexibility to the resulting cured material.

The polyoxyalkylene polymer (A) may have a normal chain or a branchedchain, or a mixed structure of these chains. Although thepolyoxyalkylene polymer (A) may contain another monomer unit, it ispreferable that this monomer contain at least 50 percent by weight, morepreferably at least 80 percent by weight, of a repeating unit expressedby —CH(CH₃)—CH₂—O—, from the viewpoint of obtaining good workability andgiving a flexibility to the resulting cured material.

The functional group containing silicon (reactive silicon group) of thepolyoxyalkylene polymer (A) which can be crosslinked by forming asiloxane bond has been generally known, and it can be crosslinked evenat room temperature. A typical reactive silicon group is expressed byFormula (III):

(wherein R⁶ represents a substituted or unsubstituted monovalent organicgroup having a carbon number in the range of 1 to 20, preferably amonovalent hydrocarbon group, or a triorganosiloxy group, and if thenumber of groups R⁶ is at least two, they may be the same or different;Y represents the hydroxy group or a hydrolyzable group, and if thenumber of groups Y is at least two, they may be the same or different; arepresents an integer of 0, 1, or 2 and b represents an integer of 1, 2,or 3, while the relationship a=2 and b=3 does not hold; and m representsan integer in the range of 0 to 18). From the viewpoint of economicalefficiency, preferably, the reactive silicon group is expressed byFormula (IV):

(where R⁶ is the same as above, and n represents an integer of 0, 1, or2).

Exemplary hydrolyzable groups expressed by Y in Formulas (III) and (IV)include halogen, hydrogen, alkoxyl, acyloxy, ketoximate, amino, amido,aminoxy, mercapto, and alkenyloxy. Among these groups, alkoxyl groups,such as methoxy and ethoxy, are preferable from the viewpoint of mildhydrolysis.

Exemplary groups expressed by R⁶ in Formulas (III) and (IV) includealkyl groups having a carbon number in the range of 1 to 20, such asmethyl and ethyl, cycloalkyl groups having a carbon number in the rangeof 3 to 20, such as cyclohexyl, aryl groups having a carbon number inthe range of 6 to 20, such as phenyl, and aralkyl groups having a carbonnumber in the range of 7 to 20, such as benzyl. R⁶ may also be atriorganosiloxy group expressed by the formula (R⁶)₃SiO—, wherein R⁶ isthe same as above. In particular, R⁶ in Formulas (III) and (IV) ispreferably the methyl group from the viewpoint of ensuring anappropriate reactivity.

Preferably, the polyoxyalkylene polymer (A) has at least one reactivesilicon group, and more preferably 1.1 to 5 reactive silicon groups, inits molecule on an average. A polyoxyalkylene polymer (A) having lessthan one reactive silicon group in its molecule makes the curingproperties insufficient and does not provide good rubber elasticity. Onthe other hand, a number of reactive silicon groups of more than 5causes the resulting cured material to be hardened and degrades theadaptability to joints, disadvantageously.

The reactive silicon group may be present at an end of the chain of thepolyoxyalkylene polymer (A) or inside the chain. If the reactive silicongroup is present at the end of the chain, the number of the effectivenetwork chains of the polyoxyalkylene polymer (A) contained in theresulting cured material is increased. Accordingly, a rubbery curedmaterial can be easily provided, exhibiting a higher strength andelongation and a lower elasticity.

The number average molecular weight (Mn) of the polyoxyalkylene polymer(A) is not particularly limited, but normally in the range of 500 to100,000, preferably in the range of 2,000 to 60,000, and more preferablyin the range of 5,000 to 30,000, from the viewpoint of the viscosity ofthe polymer and the rubber elasticity of the resulting cured material.In the present invention, the number average molecular weight of thepolyoxyalkylene polymer (A) was obtained in terms of polystyrene by gelpermeation chromatography (GPC).

Preferably, the polyoxyalkylene polymer (A) having the reactive silicongroup is prepared by introducing the reactive silicon group to apolyoxyalkylene polymer having a functional group. The polyoxyalkylenepolymer having a functional group is prepared by common polymerization(anionic polymerization using an alkali hydroxide) for producingpolyoxyalkylene polymers or chain elongation using this polymer as thestarting material, and besides by processes disclosed in, for example,Japanese Unexamined Patent Application Publication Nos. 61-197631,61-215622, 61-215623, and 61-218632 and Japanese Examined PatentApplication Publication Nos. 46-27250 and 59-15336.

The reactive silicon group may be introduced by a known method.Specifically, the following methods may be applied.

(1) A polyoxyalkylene polymer having a hydroxy group at its end isallowed to react with an organic compound having an active groupreactive to the hydroxy group and an unsaturated group, and the productis allowed to react with a hydrosilane having a reactive silicon groupto introduce the reactive silicon group to the end of the polymer.

(2) A polyoxyalkylene polymer having a functional group (hereinafterreferred to as a Z functional group), such as hydroxy, epoxy, orisocyanate, is allowed to react with a compound having a reactivesilicon group and a functional group (hereinafter referred to as a Z′functional group) reactive to the Z functional group to introduce thereactive silicon group to the end of the polymer.

Exemplary silicon compounds having a Z′ functional group and a reactivesilicon group include, but not limited to, amino group-containingsilanes, such as γ-(2-aminoethyl)aminopropylmethoxysilane,γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, andγ-aminopropyltriethoxysilane; mercapto group-containing silanes, such asγ-mercaptopropyltrimethoxysilane andγ-mercaptopropylmethyldimethoxysilane; epoxysilanes, such asγ-glycidoxypropyltrimethoxysilane andβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinyl-type unsaturatedgroup-containing silanes, such as vinyltriethoxysilane,γ-methacryloyloxypropyltrimethoxysilane, andγ-acryloyloxypropylmethyldimethoxysilane; chlorine atom-containingsilanes, such as γ-chloropropyltrimethoxysilane; isocyanate-containingsilanes, such as γ-isocyanatepropyltriethoxysilane andγ-isocyanatepropylmethyldimethoxysilane; and hydrosilanes, such asmethyldimethoxysilane, trimethoxysilane, and methyldiethoxysilane.

It is preferable to apply method (1) or a process of method (2) ofallowing a polyoxyalkylene polymer having a hydroxy group at its end toreact with a compound having an isocyanate group and a reactive silicongroup, from the viewpoint of economical efficiency and reactionefficiency.

Any type of (meth)acrylic ester copolymers having a hindered aminestructure may be used as the (meth)acrylic ester copolymer (hereinafterreferred to as the copolymer (B)) in the present invention, as long asit has a chain formed by substantially copolymerizing at least twoselected from among (meth)acrylic eater monomers, and a hindered amminestructure.

Preferably, a (meth)acrylic ester monomer unit of the copolymer (B) isexpressed by Formula (V):

(where R⁷ represents an alkyl group; R⁸ represents a hydrogen atom or amethyl group; and if R⁸ is a hydrogen atom, the monomer unit expressedby Formula (V) refers to an alkyl acrylate monomer unit).

The alkyl group of the (meth)acrylic ester monomer is not particularlylimited, and may have a normal chain or a branched chain. Normally, thealkyl group has a carbon number in the range of 1 to 30.

Preferably, the copolymer (B) is prepared by copolymerizing monomershaving an alkyl group with a carbon number of at least 8 (morepreferably in the range of 10 to 20) in order to ensure compatibilitywith component (A).

The chain of the copolymer (B) is substantially composed of alkyl(meth)acrylate monomer units. The word “substantially” here means thatthe copolymer (B) contains more than 50 percent by weight of alkyl(meth)acrylate monomer units in total relative to the total amount ofthe monomer units in the copolymer (B). More preferably, the amount ofalkyl (meth)acrylate monomer units is at least 70 percent by weight.

The copolymer (B) may contain other monomer units in addition to thealkyl (meth)acrylate monomer units. Specifically, those monomer unitsmay contain a carboxylic group, such as an acrylic or methacrylic group;an amido group, such as an acrylamido, methacrylamido,N-methylolacrylamido, or N-methylolmethacrylamido group; an epoxy group,such as glycidyl acrylate or glycidyl methacrylate; and an amino group,such as diethylaminoethyl acrylate, diethylaminoethyl methacrylate, oraminoethyl vinyl ether, or they may be derived from acrylonitrile,styrene, alpha-methylstyrene, alkyl vinyl ether, vinyl chloride, vinylacetate, vinyl propionate, or ethylene.

Preferably, the number average molecular weight (Mn) of the copolymer(B) is in the range of 1,000 to 60,000. A copolymer (B) having a numberaverage molecular weight of more than 60,000 has a high viscosity, andis accordingly difficult to manufacture. On the other hand, a numberaverage molecular weight of less than 1,000 undesirably results in abrittle cured material. The number average molecular weight of thecopolymer (B) of the present invention was obtained in terms ofpolystyrene by gel permeation chromatography (GPC).

The copolymer (B) can be prepared by vinyl polymerization, for example,by vinyl polymerization using a radical reaction in which a monomermixture is polymerized by solution polymerization, bulk polymerization,and other conventional processes. Specifically, a monomer mixture andoptionally a radical initiator or the like are allowed to react at atemperature in the range of 50 to 150° C., optionally together with achain transfer agent, such as n-dodecylmercaptan or t-dodecylmercaptan.A solvent may or may not be used. If it is used, nonreactive solvents,such as ethers, hydrocarbons, and acetic esters, are preferable from theviewpoint of sufficiently dissolving the monomer units.

Preferably, the copolymer (B) contains a reactive silicon group from theviewpoint of the curing properties and rubber elasticity. Exemplarygroups as the reactive silicon group in the copolymer (B) include thesame functional groups as the reactive silicon group in thepolyoxyalkylene polymer (A), and the reactive silicon groups of thepolyoxyalkylene polymer (A) and the copolymer (B) may be the same ordifferent.

Preferably, the copolymer (B) has at least one reactive silicon group,more preferably 1.1 to 5, and still more preferably 1.1 to 3, in itsmolecule on an average. A copolymer (B) having less than one reactivesilicon group in its molecule makes the curing properties insufficientand does not provide good rubber elasticity. On the other hand, a numberof the reactive silicon groups of more than 5 hardens the resultingcured material to reduce the elongation undesirably.

The reactive silicon group may be present at an end of the chain of thecopolymer (B) or inside the chain. If the reactive silicon group ispresent at an end of the chain, the number of the effective networkchains of the copolymer (B) contained in the resulting cured material isincreased, and accordingly a rubbery cured material can be easilyprovided, exhibiting a higher strength and elongation and a lowerelasticity. Preferably, a number of the reactive silicon group arepositioned so that the apparent number average molecular weight is inthe range of 300 to 30,000, and more preferably in the range of 3,000 to20,000, for each reactive silicon group molecule.

For introducing the reactive silicon group to the copolymer (B), variousmethods may be applied. For example, (i) a compound containing apolymerizable unsaturated bond and a reactive silicon group (forexample, CH₂═CHSi(OCH₃)₃) is added to a monomer mixture to copolymerize;or (ii) a compound (for example, an acrylic acid) having a polymerizableunsaturated bond and a reactive functional group (hereinafter referredto as a Z group) is added to a monomer mixture to copolymerize, and theresulting copolymer is allowed to react with a compound (for example, acompound having a —Si(OCH₃)₃ group and an isocyanate group) having areactive silicon group and a functional group (hereinafter referred toas a Z′ group) reactive to the Z group.

The compound having a polymerizable unsaturated bond and a reactivesilicon group used in method (i) may be expressed by Formula (VI):

(wherein R⁹ represents an organic group containing a polymerizableunsaturated bond, and R⁶, Y, a, b, and m are the same as above).Preferred one among the compounds expressed by Formula (VI) is expressedby, for example, Formula (VII):

(wherein R⁸, Y, and n are the same as above, and Q represents a divalentorganic group, such as —COOR¹⁰— (R¹⁰ represents a divalent alkylenegroup having a carbon number in the range of 1 to 6, such as —CH₂ or—CH₂CH₂—), —CH₂C₆H₄CH₂CH₂—, or —CH₂OCOC₆H₄COO(CH₂)₃—, or a direct bond.)

Exemplary compounds expressed by Formula (VI) or (VII) include:

These compounds having a polymerizable unsaturated bond and a reactivesilicon group can be prepared by various processes. For example,acetylene, allyl acrylate, allyl methacrylate, or diallyl phthalate isallowed to react with methyldimethoxysilane or methyldichlorosilane inthe presence of a Group VIII transition metal complex catalyst. Thetransition metal complex catalyst is advantageously selected from thecompounds of Group VIII transition metals consisting of platinum,rhodium, cobalt, palladium, and nickel.

There are various combinations of Z and Z′ groups in method (ii), and anexample is the combination of a vinyl group as the Z group and ahydrosilicon group (Si—H) as the Z′ group. In this combination, the Zgroup and the Z′ group are bonded by hydrosilylation.

Exemplary compounds having a polymerizable unsaturated bond and a vinylgroup as the Z group include allyl acrylate, allyl methacrylate, diallylphthalate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate,1,5-pentanediol diacrylate, 1,5-pentanediol dimethacrylate,1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, polyethyleneglycol diacrylate, polyethylene glycol dimethacrylate, polypropyleneglycol diacrylate, polypropylene glycol dimethacrylate, divinylbenzene,and butadiene. A typical compound having a reactive silicon group and ahydrosilicon group as the Z′ group is expressed by Formula (VIII):

(wherein R⁶, Y, a, b, and m are the same as above) Exemplary compoundsexpressed by Formula (VIII) include halogenated silanes, such astrichlorosilane, methyldichlorosilane, dimethylchlorosilane, andtrimethylsiloxydichlorosilane; alkoxysilanes, such as trimethoxysilane,triethoxysilane, methyldimethoxysilane, phenyldimethoxysilane, and1,3,3,5,5,7.7-heptamethyl-1,1-dimethoxytetrasiloxane; acyloxysilanes,such as methyldiacetoxysilane and trimethylsiloxymethylacetoxysilane;ketoxymatesilanes, such as bis(dimethylketoximate)methylsilane,bis(cyclohexylketoximate)methylsilane, andbis(diethylketoximate)trimethylsiloxysilane; hydrosilanes, such asdimethylsilane, trimethylsiloxymethylsilane, and1,1-dimethyl-2,2-dimethyldisiloxane; and alkenyloxysilanes, such asmethyltri(isopropenyloxy)silane.

Highly reactive halogenated silanes prepared from inexpensive bases arereadily used as the compound having a reactive silicon group and ahydrosilicon group acting as the Z′ group. The copolymer (B) resultingfrom the use of halogenated silanes can be rapidly cured at roomtemperature by being exposed to the air, while generating hydrogenchloride. However, the hydrogen chloride causes problems of irritatingodor and corrosion, and the use of halogenated silanes is thereforelimited in practice. Accordingly, it is preferable that the halogen atomof the copolymer (B) is replaced with a hydrolyzable group or a hydroxygroup. Exemplary hydrolyzable groups include alkoxyl, acyloxy, aminoxy,phenoxy, thioalkoxy, and amino.

For substituting an alkoxyl group for the halogen atom, the copolymer(B) is allowed to react with, for example, alcohol or phenol, such asmethanol, ethanol, 2-methoxyethanol, sec-butanol, tert-butanol, orphenol; an alkali metal salt of alcohol or phenol; or an alkylorthoformate, such as methyl orthoformate or ethyl orthoformate.

For substituting an acyloxy group for the halogen atom, the copolymer(B) is allowed to react with, for example, a carboxylic acid, such asacetic acid, propionic acid, or benzoic acid; or an alkali metal salt ofa carboxylic acid.

For substituting an aminoxy group for the halogen atom, the copolymer(B) is allowed to react with, for example, a hydroxylamine, such asN,N-dimethylhydroxylamine, N,N-diethylhydroxylamine,N,N-methylphenylhydroxylamine, or N-hydroxypyrrolidine; or an alkalimetal salt of a hydroxylamine.

For substituting a thioalkoxy group for the halogen atom, the copolymer(B) is allowed to react with, for example, a thioalcohol or thiophenol,such as ethylmercaptan or thiophenol; an alkali metal salt of athioalcohol or thiophenol.

For substituting an amino group for the halogen atom, the copolymer (B)is allowed to react with, for example, a primary or secondary amine,such as N,N-dimethylamine, N,N-methylphenylamine, or pyrrolidine; or analkali metal salt of a primary or secondary amine.

In addition to the halogen atom, other groups including alkoxyl andacyloxy groups may be replaced with a hydrolyzable or hydroxy group,such as amino or aminoxy, if necessary. The hydrolyzable group of thesilyl group is replaced with another hydrolyzable group suitably at atemperature in the range of 50 to 150° C. Those substitutions can becarried out regardless of whether a solvent is used or not. If a solventis used, nonreactive solvents, such as ethers, hydrocarbons, and aceticesters, are suitable from the viewpoint of sufficiently dissolving theraw materials.

The copolymer (B) has a hindered amine structure. The hindered aminestructure has a reaction-hindering substituent at the 2- and/or6-position carbon of piperidine. In a typical hindered amine structure,methyl groups are substituted for all the hydrogens at the 2- and6-position carbons.

In order to introduce a hindered amine structure to a (meth)acrylicester copolymer, at least one of its monomers is a reactive(polymerizable) hindered amine compound.

Preferably, the reactive hindered amine compound is expressed by Formula(I):

(wherein R¹ represents a hydrogen atom or an alkyl group having a carbonnumber in the range of 1 to 18, R² represents a hydrogen atom or a cyanogroup, R³ represents a hydrogen atom or an alkyl group having a carbonnumber of 1 or 2, R⁴ represents a hydrogen atom or an alkyl group havinga carbon number of 1 or 2, and X represents an oxygen atom or an iminogroup). Examples of such hindered amine compounds include, but notlimited to, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate,1,2,2,6,6-pentamethyl-4-piperidyl acrylate,2,2,6,6-tetramethyl-4-piperidyl methacrylate,2,2,6,6-tetramethyl-4-piperidyl acrylate,1,2,2,6,6-pentamethyl-4-iminopiperidyl methacrylate,2,2,6,6-tetramethyl-4-iminopiperidyl methacrylate,4-cyano-2,2,6,6-tetramethyl-4-piperidyl methacrylate, and4-cyano-1,2,2,6,6-pentamethyl-4-piperidyl methacrylate.

By allowing the copolymer (B) to hold a hindered amine structure, thehindered amine acts effectively according to its amount used, and thusthe resulting cured material can exhibit superior weather resistance fora long time.

Preferably, the amount of the reactive hindered amine compound used isat least 0.5 percent by weight, and more preferably at least 1 percentby weight, relative to the total amount of the monomers constituting thecopolymer (B). Most preferably, at least 2 percent by weight is used.Preferably, the amount of reactive hindered amine compound is 10 percentby weight or less, and more preferably 5 percent by weight or less. Acopolymerized reactive hindered amine compound content of more than 10percent by weight may negatively affect the storage stability of theresulting resin. Use of less than 0.5 percent by weight of reactivehindered amine compound may disadvantageously reduce the effect ofenhancing the weather resistance.

The above reactive hindered amine compounds may be used singly, or atlest two compounds may be copolymerized.

Preferably, the composition of the present invention contains 0.5 to 10parts by weight of monomer containing the hindered amine structurederived from the reactive hindered amine compound, relative to 100 partsby weight of polyoxyalkylene polymer (A).

The copolymer (B) may not contain any UV-absorbable structure, such asthat of benzotriazole, bisbenzotriazol, or triamidine.

In the present invention, the most preferred form of the copolymer (B)has a structure prepared by copolymerizing only the combinationconsisting of an alkyl (meth)acrylate, a compound having a polymerizableunsaturated bond and a reactive silicon group, and a reactive hinderedamine compound.

Preferably, the content of the copolymer (B) in the curable compositionof the present invention is at least 20 parts by weight, more preferablymore than 20 parts by weight, and still more preferably at least 25parts by weight, relative to 100 parts by weight of the polyoxyalkylenepolymer (A) from the viewpoint of workability and the rubber elasticityof the curable composition. The upper limit is preferably 1,000 parts byweight, and more preferably 200 parts by weight.

The curable composition may contain a curing accelerator. Exemplarycuring accelerators include, but not particularly limited to, titanateesters, such as tetrabutyl titanate and tetrapropyl titanate; tincarboxylates, such as dibutyltin dilaurate, dibutyltin maleate,dibutyltin diacetate, tin octylate, and tin naphthenate; organic tincompounds, such as products by a reaction of dibutyltin oxide with aphthalate ester and dibutyltin acetylacetonate; organic aluminiumcompounds, such as aluminium tris(acetylacetonate), aluminiumtris(ethylacetoacetate), and diisopropoxyaluminium ethylacetoacetate;chelate compounds, such as zirconium tetraacetylacetonate and titaniumtetraacetylacetonate; lead octylate; amines, such as butylamine,octylamine, laurylamine, dibutylamine, monoethanolamine, diethanolamine,triethanolamine, diethylenetriamine, triethylenetetraamine, oleylamine,cyclohexylamine, benzylamine, diethylaminopropylamine, xylylenediamine,triethylenediamine, guanidine, diphenylguanidine,2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine,2-ethyl-4-methylimidazole, and 1,8-diazabicyclo(5.4.0)undecen-7 (DBU),and salts of these amines and carboxylic acids or the like; lowmolecular weight polyamide resins prepared from an excessive amount ofpolyamine and a polybasic acid; products by a reaction of an excessiveamount of polyamine with an epoxy compound; silanol condensationcatalysts, such as silane coupling agents containing an amino group,including γ-aminopropyltrimethoxysilane andN-(β-aminoethyl)aminopropylmethyldimethoxysilane; and other knownsilanol condensation catalysts, including acid catalysts and basiccatalysts. These catalysts may be used singly or in combination.

The curing accelerator is used preferably in an amount in the range of0.1 to 20 parts by weight to 100 parts by weight of the total of thepolyoxyalkylene polymer (A) and the copolymer (B), and more preferablyin the range of 1 to 10 parts by weight. An amount of the curingaccelerator of less than 0.1 parts by weight may reduce curing rate andmake the progress of curing reaction hard. On the other hand, an amountof the curing accelerator of more than 20 parts by weight causes heat orbubbles to be locally generated during curing, and consequently itbecomes difficult to provide a superior cured material.

In use of the curable composition of the present invention, a filler mayalso be used optionally, and such fillers include reinforcements, suchas fume silica, precipitable silica, silicic acid anhydride, hydroussilicic acid, and carbon black; other fillers, such as calciumcarbonate, magnesium carbonate, diatomaceous earth, fired clay, clay,talc, titanium oxide, bentonite, organic bentonite, iron (III) oxide,zinc oxide, active hydrozincite, hydrogenated castor oil, andShirasu-balloons; and fibrous fillers, such as asbestos, glass fiber,and filament.

For a particularly strong cured composition, 1 to 100 parts by weight offiller is used relative to 100 parts by weight of the total of thepolyoxyalkylene polymer (A) and the copolymer (B) and the filler isselected from among fume silica, precipitable silica, silicic acidanhydride, hydrous silicic acid, carbon black, surface-treated finecalcium carbonate, fired clay, clay, active hydrozincite, and so forth.Thus, a satisfactory result is produced.

For a low-strength, high-elongation cured composition, 5 to 200 parts byweight of filler is used relative to 100 parts by weight of the total ofthe polyoxyalkylene polymer (A) and the composition (B) and the filleris selected from among titanium oxide, calcium carbonate, magnesiumcarbonate, talc, iron (III) oxide, zinc oxide, Shirasu-balloons, and soforth. Thus, a satisfactory result is produced.

The above-enumerated fillers may be used singly or in combination.

Use of a plasticizer in combination with filler in the curablecomposition of the present invention leads to an increased elongationand allows a large amount of filler to be blended, advantageously.Exemplary plasticizers include phthalate esters, such as dioctylphthalate, dibutyl phthalate, and butylbenzyl phthalate; aliphaticdibasic esters, such as dioctyl adipate, isodecyl succinate, and dibutylsebacate; glycol esters, such as diethylene glycol dibenzoate, andpentaerythritol esters; aliphatic esters, such as butyl oleate andmethyl acetylricinolate; phosphate esters, such as tricresyl phosphate,trioctyl phosphate, and octyldiphenyl phosphate; epoxy plasticizers,such as epoxidized soybean oil, epoxidized linseed oil, and benzylepoxystearate; polyester plasticizers such as polyesters of dibasicacids and dihydric alcohols; polyethers, such as polypropylene glycoland its derivatives; polystyrenes, such as poly(alpha-methylstyrene) andpolystyrene; polybutadiene; butadiene-acrylonitrile copolymers;polychloroprene; polyisoprene; polybutene; and chlorinated paraffins.These plasticizers may be used singly or in combination.

The plasticizer is used preferably in an amount in the range of 0 to 100parts by weight relative to 100 parts by weight of the total of thepolyoxyalkylene polymer (A) and the copolymer (B).

In addition, various additives may be optionally used, such as anadhesion improver, a physical property adjuster, a storage stabilityimprover, an antioxidant, a UV absorber, a metal-inactivating agent, anozone degradation inhibitor, a light stabilizer, an amine-based radicalchain terminator, a phosphorous peroxide decomposer, a lubricant, apigment, and a blowing agent.

The process for preparing the curable composition of the presentinvention is not particularly limited, and common processes may beapplied. For example, the above-described constituents may be blendedand kneaded with a mixer, roll, or kneader at room temperature or withheating, or the constituents may be dissolved in a small amount of asuitable solvent to mix. Alternatively, a one-part or two-partcomposition may be used which comprises a combination appropriatelyincluding some of those constituents.

The curable composition of the present invention exposed to the airforms a three-dimensional network structure by the action of water, andthus cured into a solid having a rubber elasticity. The curablecomposition of the present invention can be used as elastic sealants,especially as building sealants, siding board sealants, and glazingsealants, in buildings, ships, automobiles, and roads. In addition,since the curable composition adheres, singly or with help of primer, toa wide variety of substrates, such as glass, porcelain, wood, metal, andresin compositions, it can be used for various types of sealingcomposition and adhesive composition. In application to adhesive, thecurable composition can be used for one-part adhesives, two-partadhesives, contact adhesives which adhere after open time, and besides,it will be useful for paint, waterproof coating, food packagingmaterial, cast rubber, material for making molds, and expanded material.

For use of the curable composition as building sealants and siding boardsealants, it is preferable that the resulting cured material exhibit nocrack in its surface for a long time through an accelerated weatherresistance test using a sunshine WOM. The crack here refers to anobvious crack observed in a visual inspection of the surface state of asheet after being exposed without load or deformation.

If a crack occurs in the resulting cured material in the acceleratedweather resistance test using a sunshine WOM, the curable composition islikely to result in a defiled sealant in use for highlyweather-resistant siding boards.

The weather resistance of the curable composition of the presentinvention can be set in combination with the constituents (A) and (B)and other constituents, especially antioxidant and UV absorber, whilebalancing with other practical properties.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further described in detail with referenceto the following examples, but the present invention is not limited tothe examples. The number average molecular weight of each polymer wasobtained in terms of polystyrene by gel permeation chromatography (GPC).

SYNTHESIS EXAMPLE 1

In a reaction vessel equipped with a stirrer was placed 800 g of apolyoxyalkylene with an average molecular weight of about 19,000 havingan allyl ether group at an end of its molecular chain and subsequently1×10⁻⁴ [eq./vinyl group] of methyldimethoxysilane and chloroplatiniccatalyst (chloroplatinic acid hexahydrate). Thus a reaction wasperformed at 90° C. for 2 hours. The resulting polymer was subjected to¹H-NMR analysis, and the proportion of a functional group at the end inthe resulting polymer was about 77% (polymer A).

SYNTHESIS EXAMPLE 2

A solution containing 68 g of butyl acrylate, 8 g of methylmethacrylate, 20 g of stearyl methacrylate, 2 g ofγ-methacryloxypropylmethyldimethoxysilane, 2 g of1,2,2,6,6-pentamethyl-4-piperidinyl-methacrylate, 0.5 g of V-59(produced by Wako Pure Chemical Industries), and 20 g of toluene wasdripped into 50 g of toluene heated to 110° C. over a period of 4 hoursto prepare a solution of a copolymer (polymer B) having a number averagemolecular weight of about 18,000 in toluene.

SYNTHESIS EXAMPLE 3

A solution containing 64g of butyl acrylate, 8 g of methyl methacrylate,20 g of stearyl methacrylate, 6g ofγ-methacryloxypropylmethyldimethoxysilane, 2 g of1,2,2,6,6-pentamethyl-4-piperidinyl-methacrylate, 2.2 g of V-59(produced by Wako Pure Chemical Industries), and 20 g of toluene wasdripped into 50 g of toluene heated to 110° C. over a period of 4 hoursto prepare a solution of a copolymer (polymer C) having a number averagemolecular weight of about 8,000 in toluene.

SYNTHESIS EXAMPLE 4

A solution containing 68 g of butyl acrylate, 10 g of methylmethacrylate, 20 g of stearyl methacrylate, 2 g ofγ-methacryloxypropylmethyldimethoxysilane, 0.5 g of V-59 (produced byWako Pure Chemical Industries), and 20 g of toluene was dripped into 50g of toluene heated to 110° C. over a period of 4 hours to prepare asolution of a copolymer (polymer D) having a number average molecularweight of about 18,000 in toluene.

SYNTHESIS EXAMPLE 5

A solution containing 64 g of butyl acrylate, 10 g of methylmethacrylate, 20 g of stearyl methacrylate, 6 g ofγ-methacryloxypropylmethyldimethoxysilane, 2.2 g of V-59 (produced byWako Pure Chemical Industries), and 20 g of toluene was dripped into 50g of toluene heated to 110° C. over a period of 4 hours to prepare asolution of a copolymer (polymer E having a number average molecularweight of about 8,000 in toluene.

EXAMPLE 1

Polymer A, as constituent (A), prepared in Synthesis Example 1 and thesolution of polymer B, as constituent (B), in toluene prepared inSynthesis Example 2 were bended at a ratio (weight ratio) of 70/30 on asolid content basis, and heated under reduced pressure to remove thetoluene. Thus, a transparent, viscous liquid was prepared. With 100 g ofthis resulting mixture were blended 140 g of colloidal calcium carbonate(produced by Shiraishi Kogyo, trade name: Hakuenka CCR), 13 g of□groundcalcium carbonate (produced by Shiraishi Calcium, trade name: Whiton SB), 86 g of a plasticizer (produced by Takeda Chemical Industries, tradename: Actcol P-23), 20 g of titanium oxide (produced by Ishihara Sangyo,trade name: Tipaque R-820), 2 g of an amide wax (produced by KusumotoChemicals, trade name: Disparlon 6500), 1 g of a benzotriazole UVabsorbent b(produced by Ciba Specialty Chemicals, trade name: Tinuvin327), and 0.5 g of carbon black (produced by Asahi Carbon, trade name:Carbon #70), and kneaded well with a triple paint roll to prepare a mainagent. With the main agent were further blended 2 g ofvinylmethoxysilane (produced by Nippon Unicar, trade name: A171), 3 g of3-aminoethyl 3-aminopropyltrimethoxysilane (produced by Nippon Unicar,trade name: A-1120), and 2 g of dibutyltin diacetylacetonate (producedby Nitto Kasei, trade name: Neostann U-220) to prepare a compound.

The compound was formed into a sheet with a thickness of 3 mm, allowedto stand at 23° C. for 3 days, and then heated at 50° C. for 4 days toyield a rubber sheet. The rubber sheet on an aluminium plate with athickness of 1 mm was placed in a sunshine weatherometer (produced bySuga Test Instruments) and the weather resistance was evaluated.

EXAMPLE 2

The weather resistance was evaluated in the same manner as in Example 1except that polymer C was used as constituent (B)

EXAMPLE 3

The weather resistance was evaluated in the same manner as in Example 1except that 1.25 g of an additive-type hindered amine light stabilizer,Sanol LS-770 (produced by Sankyo), was further added.

COMPARATIVE EXAMPLE 1

The weather resistance was evaluated in the same manner as in Example 1except that polymer D was used as constituent (B).

COMPARATIVE EXAMPLE 2

The weather resistance was evaluated in the same manner as in Example 1except that polymer E was used as constituent (B).

COMPARATIVE EXAMPLE 3

The weather resistance was evaluated in the same manner as in Example 1except that polymer D was used as constituent (B) and 0.74 g of anadditive-type hindered amine light stabilizer, Mark LA-63 (produced byAsahi Denka Kogyo), was further added.

COMPARATIVE EXAMPLE 4

The weather resistance was evaluated in the same manner as in Example 1,except that polymer D was used as constituent (B) and 1.25 g of anadditive-type hindered amine light stabilizer, Sanol LS-770 (produced bySankyo), was further added.

COMPARATIVE EXAMPLE 5

The weather resistance was evaluated in the same manner as in Example 1,except that polymer D was used as constituent (B) and 1.48 g of anadditive-type hindered amine light stabilizer, Mark LA-63 (produced byAsahi Denka Kogyo), was further added.

COMPARATIVE EXAMPLE 6

The weather resistance was evaluated in the same manner as in Example 1,except that polymer D was used as constituent (B) and 2.50 g of anadditive-type hindered amine light stabilizer, Sanol LS-770 (produced bySankyo), was further added.

COMPARATIVE EXAMPLE 7

The weather resistance was evaluated in the same manner as in Example 1except that the ratio (weight ratio) of constituent (A) to constituent(B) was set at 85/15 on a solid content basis.

The results are shown in Table 1. In the table, deterioration time usingSWOM means the time taken before the occurrence of a small crack in thesurface of the sample which was subjected to exposure using the sunshineweatherometer and whose surface state was observed every 100 hours.

TABLE 1 Compar- Compar- Compar- Exam- Exam- ative ative ativeComparative Comparative Comparative Comparative Example 1 ple 2 ple 3Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7Constituent Polymer A 70 70 70 70 70 70 70 70 70 85 (A) ConstituentPolymer B 30 — 30 — — — — — — 15 (B) Polymer C — 30 — — — — — — — —Polymer D — — — 30 — 30 30 30 30 — Polymer E — — — — 30 — — — — —Additive- LA-63 — — — — — 0.74 — 1.48 — — type LS-770 — — 1.25 — — —1.25 — 2.50 — hindered amine light stabilizer Deterioration time using4700 4800 4700 1600 1700 1800 1700 1900 1700 800 SWOM (hour)

The results show that the curable compositions of Examples 1 to 3, whichcontain the copolymer (B) having a hindered amine structure, exhibitextremely higher weather resistance than the curable compositions ofComparative Examples 1 to 6, which simply contain a hindered aminecompound.

The adhesions to a substrate of Example 1 and Comparative Examples 1, 3,and 7 were evaluated. Evaluation of the adhesion to a substrate wasconducted as follows. Compounds were each placed on surface-cleanedelectrolytically colored aluminium, acrylic-coated aluminium, glass, andvinyl chloride-coated steel and cured at 23° C. and 50% RH for 7 days.The adhesion between the resulting cured material and the substrates wasevaluated by hand peeling. After curing at 23° C. and 50% RH for 7 days,the samples were immersed in warm water of 50° C. for 7 days. Then,after the water temperature reached 23° C., the adhesion underwater-resistant conditions was evaluated in the same manner.

The results are shown in Table 2. In the table, C represents thecohesive failure of the sealant; A, peeling at the interface between thesealant and the substrate. The numbers represent their proportions andthe sum of them is 100. A larger proportion of C means a higheradhesion.

TABLE 2 Comparative Comparative Comparative Example 1 Example 1 Example3 Example 7 Constituent (A) Polymer A 70 70 70 85 Constituent (B)Polymer B 30 — — 15 Polymer C — — — — Polymer D — 30 30 — Polymer E — —— — Additive-type LA-63 — —    0.74 — hindered amine LS-770 — — — —light stabilizer Adhesion to Second electrolytic C100A0 C100A0 C100A0C100A0 substrate under colored aluminum dried conditions acrylic-coatedC70A30 C0A100 C0A100 C30A70 aluminum Glass C100A0 C100A0 C100A0 C100A0Vinyl chloride- C100A0 C100A0 C100A0 C100A0 coated steel sheet Adhesionto Second electrolytic C20A80 C0A100 C80A20 C0A100 substrate coloredaluminium water-resistant Glass C80A20 C60A40 C80A20 C80A20 conditionsVinyl chloride- C50A50 C0A100 C0A100 C40A60 coated steel sheetEvaluation result number of C0A100 0/7 3/7 2/7 1/7

Example 1 exhibits an adhesion superior to Comparative Examples 1 and 3,as shown in Table 2, in addition to superior weather resistance. Also,Comparative Example 7, which contains less than 20 parts by weight ofconstituent (B), is inferior to Example 1 in weather resistance andadhesion.

INDUSTRIAL APPLICABILITY

The present invention provides a curable composition containing apolyoxyalkylene polymer (A) having a reactive silicon group and a(meth)acrylic ester copolymer (B) having a hindered amine structure. Thecurable composition exhibits superior weather resistance for a longtime.

1. A curable composition comprising: 100 parts by weight of apolyoxyalkylene polymer (A) having at least one functional groupcontaining silicon, the functional group being crosslinked by forming asiloxane bond; and at least 25 to 1,000 parts by weight of a(meth)acrylic ester copolymer (B) having a hindered amine structure,wherein the (meth)acrylic ester copolymer (B) is formed from a monomermixture comprising (meth)acrylic ester and a copolymerizable hinderedamine compound.
 2. A curable composition according to claim 1, whereinthe (meth)acrylic ester copolymer (B) is prepared by copolymerizing areactive hindered amine compound expressed by Formula (I):

(Where R¹ represents a hydrogen atom or an alkyl group having a carbonnumber in the range of 1 to 18, R² represents a hydrogen atom or a cyanogroup, R³ represents a hydrogen atom or an alkyl group having a carbonnumber of 1 or 2, R⁴ represents a hydrogen atom or an alkyl group havinga carbon number of 1 or 2, and X represents an oxygen atom or an aminogroup).
 3. A curable composition according to claim 1, wherein at leastone of (methyl)acrylic ester monomer units constituting the(meth)acrylic ester copolymer (B) has an alkyl group having a carbonnumber of 8 or more.
 4. A curable composition according to claim 1,wherein the (meth)acrylic ester copolymer (B) is prepared bycopolymerizing a vinyl monomer containing a reactive silicon group.
 5. Acurable composition according to claim 1, wherein the functional groupcontaining silicon of the polyoxyalkylene polymer (A) is a reactivealkoxysilyl group.
 6. A curable composition according to claim 1,wherein the (meth)acrylic ester copolymer (B) contains 0.5 to 10 partsby weight of a monomer unit containing the hindered amine structurerelative to 100 parts by weight of the polyoxyalkylene polymer (A).
 7. Acurable composition according to claim 1, wherein the (meth)acrylicester copolymer (B) has a structure formed by copolymerizing only the(meth)acrylic ester, a compound having a polymerizable unsaturated bondand a reactive silicon group, and a the copolymerizable hindered aminecompound.